CONVERTIBLE FAN/SHAFT ENGINE DEMONSTRATION

The objective of this paper is to present the results of a convertible engine performance test. A turbofan engine (ASTAFAN IVG2) with variable pitch fan compressor rotor blades was modified to allow test evaluation in the convertible engine mode; i.e., either in jet thrust, pure shaft power, or any combination of thrust and shaft power. The measurements were taken in an ambient engine test cell equipped with dynamometer, thrust bed, and engine monitoring instrumentation. Simultaneous measurement of developed thrust and shaft power was obtained by mounting the dynamometer and engine assembly as a unit on the thrust bed. Data obtained over a major portion of shaft power vs. thrust operation map at sea level static conditions show that this convertible engine concept is feasible. Maximum measured values were 1650 pounds thrust and 975 shaft horsepower. Transient data were also taken and indicate that a full swing from maximum thrust/minimum power to minimum thrust/maximum power can be made with this unoptimized engine/control in less than five seconds.